JP3258219B2 - Hydraulic control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a hydraulic actuator for controlling the operation of a hydraulic lifting cylinder in a working boom.

[0002]

2. Description of the Related Art In an aerial work vehicle 10 as shown in FIG. 2, a boom 13 is provided on a vehicle body 11 such that the boom 13 can be freely raised and lowered. Made by actuation. Also, boom 1
A worktable 15 on which the worker M can board is disposed at the distal end of the work 3.

The up / down operation control of the boom 13 configured as described above (extension / extension operation control of the hydraulic up / down cylinder 16) is performed by a hydraulic operation control circuit as shown in FIG. This control circuit is configured to supply the hydraulic oil supplied from the hydraulic pump P to a hydraulic actuator such as the up-and-down cylinder 16 via a switching valve (open / close valve) 18. The hydraulic operation control circuit reduces the load on the hydraulic pump P when the undulating cylinder 16 or the like is not operating,
A hydraulic control device including a pressure compensating valve 40 and the like that causes the hydraulic oil supplied from the hydraulic pump P to flow out to the tank T is provided in order to keep the oil supply amount constant when the up-and-down cylinder 16 and the like operate.

The pressure compensating valve 40 applies pilot pressure from the pilot oil passage P1 to the spring chamber 4 in accordance with the operation of the switching valve 18.
It works by receiving 2. That is, when the switching valve 18 is in the neutral position (closed position) as shown in FIG. 3, the pilot oil passage P1 communicates with the second drain oil passage D2 connected to the tank T. Does not work. Then, the spool valve 41 is moved leftward by the hydraulic oil flowing through the first drain oil passage D1, and the hydraulic oil supplied from the pump P is discharged to the tank T through the discharge hole 41a. Therefore, when the switching valve 18 is at the neutral position, the discharge hydraulic pressure from the hydraulic pump P can be low, and the driving horsepower loss of the hydraulic pump P can be reduced.

When the switching valve 18 is switched to the left or right to supply hydraulic oil to the hydraulic up-and-down cylinder 16 (open position), the pilot oil passage P1 and the supply oil passage L1
And the pilot pressure (load pressure of the actuator) acts on the spring chamber 42. Thereby, the spool valve 41
The force to which the force of the spring 43 and the pilot pressure are applied acts in the direction to move to the right. Here, the pressure compensating valve 40 is configured to control the oil pressure of the first drain oil passage D1 and the oil pressure of the pilot oil passage P1 so that the oil pressure supplied from the hydraulic pump P to the hydraulic up / down cylinder 16 becomes a force acting on the spool valve 41. When the difference from the pressure becomes higher than the pressure set by the spring 43, the spool valve 4
By moving 1 to the left, the surplus amount of hydraulic oil supplied from the hydraulic pump P flows out from the first drain oil passage D1 to the tank T.

Here, when the boom 13 is raised and lowered (when the switching valve 18 is switched to the left or right), the movement of the worker M on the work table 15 and the inertia at the start of the operation cause the boom to move. 13 may vibrate in the undulating direction (this vibration is a gentle vibration of about 1 to 3 Hz). When such vibration occurs, the undulating cylinder 16
The force which expands and contracts this acts on (the load pressure fluctuates)
As a result, pressure fluctuation corresponding to this vibration occurs in the supply oil passage L1 and the pilot oil passage P1 of the pressure compensating valve 40.

When a pressure change occurs in the pilot oil passage P1, the pressure in the spring chamber 42 also changes in accordance with the change, whereby the spool valve 41 moves left and right in the same cycle (repeats the opening and closing operations). For this reason, the amount of hydraulic oil supplied to the up-and-down cylinder 16 increases and decreases in the same cycle, and the expansion and contraction operation is repeated, and the vibration of the boom 13 is promoted by the expansion and contraction operation of the cylinder 16, which may cause a so-called hunting state. is there.

In the conventional hydraulic operation control circuit, the throttle 45 is provided in the pilot oil passage P1 in order to prevent the boom 13 from being hunted as described above. As a result, even when the pilot pressure fluctuates, the pressure in the spring chamber 42 does not suddenly fluctuate, so that the spool 41 hardly moves due to the vibration of the boom 13.

[0009]

However, in the control circuit constructed as described above, since the throttle 45 is provided, the responsiveness (start of movement) of the pressure compensating valve 40 at the start of the expansion / contraction operation of the up / down cylinder 16 is started. There is a problem that becomes worse. That is, when the operation starts, the pressure in the spring chamber 42 rises slowly, so that the spool 41 does not immediately move rightward. During that time, a part of the hydraulic oil supplied from the pump P is discharged to the tank T through the discharge hole 41a. Therefore, the start of supply to the up-and-down cylinder 16 is delayed, and the responsiveness at the start of the expansion / contraction operation is deteriorated.

The present invention has been made in view of such a problem, and can stably operate a hydraulic actuator even if the pilot hydraulic pressure of a pressure compensating valve periodically fluctuates due to boom vibration or the like. It is another object of the present invention to provide a hydraulic control device having excellent responsiveness during operation.

[0011]

In order to solve such a problem, a hydraulic control device according to the present invention provides an on-off valve in a supply oil passage for supplying hydraulic oil from a hydraulic supply source to a hydraulic actuator. An on-off valve controls supply of hydraulic oil from a hydraulic supply source to a hydraulic actuator. A pressure compensating valve is provided in the drain oil passage branched from the hydraulic supply source and the on-off valve in the supply oil passage and connected to the tank, and opens and closes the drain oil passage. The pressure compensating valve receives the pilot pressure from the pilot oil passage and acts in the closing direction.

The pilot oil passage is connected to a tank via the on-off valve when the on-off valve is in a closed state, and is connected to a hydraulic supply source via the on-off valve when the on-off valve is in an open state. . And, a check valve that allows only the flow from the on-off valve to the pressure compensation valve is provided in the pilot oil passage,
A predetermined gap is formed between the check valve and the pressure compensating valve between the spool valve and the valve cylinder of the pressure compensating valve so that the hydraulic oil can flow out to the tank.

[0013]

According to the hydraulic control device configured as described above,
When the on-off valve is opened, hydraulic oil is supplied from a hydraulic supply source to the hydraulic actuator, and a hydraulic actuator such as a hydraulic raising / lowering cylinder can be driven. At this time, since the pilot oil passage is connected to the hydraulic pressure source, the pressure compensating valve receives the pilot pressure and acts in the closing direction, and the flow rate of the hydraulic oil from the hydraulic pressure source is adjusted and supplied to the hydraulic actuator. Since the flow of hydraulic oil from the on-off valve to the pressure compensating valve is permitted by the check valve, the pressure compensating valve acts quickly in the closing direction and does not delay operation.

Further, by closing the on-off valve,
The supply of hydraulic oil to the hydraulic actuator is cut off, and the supply of pilot pressure to the pressure compensating valve is cut off. Since the pilot oil passage is provided with a check valve, the operating oil between the check valve and the pressure compensating valve cannot flow out to the tank T via the on-off valve. The gap formed between the cylinder and the cylinder allows the hydraulic oil between the check valve and the pressure compensating valve to flow into the tank. As a result, the pilot pressure does not act on the pressure compensating valve, the drain oil passage is opened, and the hydraulic oil is discharged to the tank.

When the load acting on the hydraulic actuator temporarily changes while the hydraulic actuator is operated by opening the on-off valve, the pressure in the supply oil passage and the pilot oil passage becomes higher than the supply oil pressure. It goes up and down. Here, even if the pressure in the supply oil passage and the pilot oil passage becomes higher than the supply oil pressure, the force acting in the direction in which the pressure compensating valve closes does not relatively change, so that the operation of the spool valve has no effect. I will not receive it. Also, even if the pressure in the supply oil passage and the pilot oil passage is lower than the supply oil pressure, the check valve is closed, so the pilot pressure between the check valve and the pressure compensating valve does not decrease, which affects the operation of the spool valve. Hard to receive. Thus, even if the pilot oil pressure changes, the hydraulic actuator can be operated stably.

[0016]

Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows an aerial work vehicle 10 provided with a fluid pressure control device according to the present invention. The aerial work vehicle 10 is provided with a swivel table 12 that can freely turn horizontally with respect to a vehicle body 11, and a boom 13 that can freely move up and down and extend and contract is provided on the swivel table 12. . The boom 13 includes a base boom member 13a, an intermediate boom member 13b, and a distal boom member 13c.
It is telescopic (nested) and telescopic. The raising and lowering operation of the boom 13 is performed by the proximal boom member 13a.
Hydraulic raising and lowering cylinder 16 disposed between
Made by the telescopic operation. Also, the tip boom member 1
At the tip of 3c, a worktable 15 configured to allow the worker M to board is arranged.

In the aerial work vehicle 10 constructed as described above, the control of the raising and lowering operation of the boom 13, that is, the control of the expansion and contraction of the hydraulic raising and lowering cylinder 16 is performed by a hydraulic operation control circuit as shown in FIG. The control circuit includes a supply oil passage L1 connecting a hydraulic pump (hydraulic supply source) P and a hydraulic up / down cylinder (hydraulic actuator) 16, and a supply of hydraulic oil to the hydraulic up / down cylinder 16 provided in the supply oil passage L1. A switching valve (opening / closing valve) 18 for performing discharge control, a drain oil passage D1 branched from the hydraulic pump P and the switching valve 18 in the supply oil passage L1 and connected to the tank T, and a drain oil passage D1
Pressure compensating valve 2 which is provided at the opening and closing the drain oil passage D1
0, the pilot oil passage P1 having one end connected to the pressure compensating valve 20 and the other end connected to the switching valve 18, and only the flow from the switching valve 18 provided in the pilot oil passage P1 to the pressure compensating valve 20. And a check valve 30 that allows the hydraulic control.

A description will be given of a case in which the operation of the hydraulic hoist cylinder 16 is controlled using the hydraulic control device configured as described above. First, a description will be given of a case where the switching valve 18 in which the operation of the hydraulic up / down cylinder 16 is not performed is in the closed state (neutral position). In this case, the pilot line P1 connected to the spring chamber 22 of the pressure compensating valve 20 is connected to the switching valve 1
8 and communicate with the second drain oil passage D2. For this reason,
When a force greater than the urging force of the spring 23 acts on the spool valve 21 by the hydraulic oil flowing through the first drain oil passage D1, the spool valve 21 moves to the left to open the first drain oil passage D1, and the pump P The supplied hydraulic oil is discharged to the tank T through the discharge hole 21a, and the load on the pump P is reduced.

When the extension operation of the hydraulic raising / lowering cylinder 16 is performed, the switching valve 18 is moved to the left to supply hydraulic oil to the bottom side supply oil passage L1a. In this state, the supply oil passage L1 and the pilot oil passage P1 are connected via the switching valve 18, and the pilot pressure acts on the spring chamber 22.

As a result, the oil pressure in the spring chamber 22 and the oil pressure in the first drain oil passage D1 become equal, and the spool 21 immediately moves rightward by the urging force of the spring 22. Here, if the amount of oil required for the extension operation of the hydraulic undulating cylinder 16 matches the amount of oil supplied from the hydraulic pump P, the first drain oil passage D1 is closed, and the hydraulic oil supplied from the hydraulic pump P is closed. Is excessive, the excess is discharged to the tank T. Therefore, the hydraulic oil is supplied from the hydraulic pump P to the hydraulic up-and-down cylinder 16 without waste, and a quick extension operation is performed. In order to perform the contraction operation of the hydraulic raising / lowering cylinder 16, the switching valve 18 is moved to the right to supply the hydraulic oil to the rod-side supply oil passage L1b. The supply-side check valve C and the pressure-reducing valve R1 are provided upstream of the switching valve 18 in the supply oil passage L1.
Is provided.

After the hydraulic valve 16 is extended or retracted by moving the switching valve 18 to the left or right in this manner, the supply of the hydraulic oil is stopped by setting the switching valve 18 to the neutral position, and the boom 13 is turned off. At a desired undulation angle. At this time, the operating oil between the check valve 30 and the switching valve 18 in the pilot oil passage P1 is discharged from the second drain oil passage D2 to the tank T, but the operation oil between the check valve 30 and the pressure compensating valve 20 is operated. The oil is not discharged from the second drain oil passage D2 to the tank T by the action of the check valve 30, and the oil is not discharged from the spool valve 21 and the valve cylinder 24.
And is gradually discharged to the tank T through the gap 25 formed between them.

As a result, the spool valve 21 slowly moves to the left to open the first drain oil passage D1, and the operating oil supplied from the pump P can be discharged to the tank T through the discharge hole 21a. The load can be reduced. Here, even if the leftward movement of the spool valve 21 is slow, only the movement until the first drain oil passage D1 is opened becomes slow, which has no effect on the operation of the hydraulic up / down cylinder 16. There is no.

Next, the worker M on the work table 15 with the hydraulic up-and-down cylinder 16 being extended and retracted.
The case where the boom 13 vibrates in the up-and-down direction due to the movement of the boom, the inertia at the start of operation, and the like will be described. When such vibration occurs, a force for expanding and contracting the same acts on the undulating cylinder 16, causing pressure fluctuations in the supply oil passage L 1 and the pilot oil passage P 1.

For example, when the hydraulic cylinder 16 is compressed by vibration while the hydraulic cylinder 16 is extended, the hydraulic pressure in the supply oil passage L1 and the pilot oil passage P1 is supplied from the hydraulic pump P. It is higher than the hydraulic pressure of the hydraulic oil. At this time, since the check valve C is closed, the oil pressure in the pilot oil passage P1 increases,
Since the oil pressure in the first drain oil passage D1 does not increase,
It is hardly affected by the operation of the pressure compensating valve 20 (spool valve 21).

The check valve C is not always necessary in the present invention. That is, when the check valve C is not provided, the oil pressure in the supply oil passage L1 increases and the oil pressure in the first drain oil passage D1 also increases. Since no significant change occurs, the operation of the spool valve 21 is not affected by the fluctuation of the hydraulic pressure.

When the hydraulic cylinder 16 is pulled, the oil pressure in the supply oil passage L1 and the pilot oil passage P1 becomes lower than the oil pressure of the hydraulic oil supplied from the hydraulic pump P. At this time, the check valve 30 is closed, the pilot pressure between the check valve 30 and the pressure compensating valve 20 does not decrease, and the oil pressure in the spring chamber 22 does not decrease. Therefore, also in this case, the operation of the spool valve 21 is hardly affected by the fluctuation of the hydraulic pressure.

At this time, the check valve 30 is closed, but the hydraulic oil in the spring chamber 22 flows out of the gap 25, whereby the pressure in the spring chamber 22 gradually decreases. However, the vibration cycle of the boom 13 as described above is about 1 to 3
Hz, the pressure in the pilot oil passage P1 decreases for a short time. Therefore, the gap 25
Is set such that the spool valve 21 does not move to the left to the extent that the spool valve 21 opens in such a time, and the outflow is slow. As a result, a change in the flow rate of the working oil supplied to the hydraulic undulating cylinder 16 can be reduced,
The boom 13 can be prevented from entering a hunting state.

In FIG. 1, a gap is shown between the outer periphery of the portion where the discharge hole 21a is formed and the valve cylinder 24 when the spool valve 21 is at the closed position (right side). The gap is only drawn large for convenience of illustration. That is, in the actual pressure compensating valve 20, this gap is a gap necessary for sliding the spool valve 21, and the discharge of the hydraulic oil from this gap can be ignored.

In the above embodiment, the case where the operation of the hydraulic up / down cylinder 16 is controlled using the hydraulic control device according to the present invention has been described. However, the supply oil passage L1, the bypass oil passage P1, and the second drain oil passage D2 The second supply oil passage L2, the second bypass oil passage P2, and the third drain oil passage D3 may be branched from each other. Then, if a hydraulic cylinder or hydraulic motor for causing the boom 13 to expand and contract and the swivel table 12 to perform a turning operation and a switching valve for controlling these operations are provided in each of these oil passages, the same as described above is provided. Control can be performed. Therefore, FIG. 1 shows a state in which a relief valve R2 and a shuttle valve S are provided for a case where a hydraulic actuator other than the hydraulic raising / lowering cylinder 16 is provided.

[0030]

As described above, according to the hydraulic control device of the present invention, the pressure compensating valve provided in the bypass oil passage branched from the supply oil passage makes it possible to control the hydraulic supply source when the hydraulic actuator is not operated. The load can be reduced. Then, when the hydraulic actuator is operated, the pilot pressure acts on the pilot oil passage without delay, so that the pressure compensating valve can be closed immediately, and the responsiveness at the time of operating the hydraulic actuator is excellent. Also, even when the pilot pressure fluctuates during the operation of the hydraulic actuator,
Since the pressure compensating valve is hardly affected by the fluctuation of the pilot pressure, the hydraulic actuator can be operated stably.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram provided with a hydraulic control device according to the present invention.

FIG. 2 is a side view of an aerial work vehicle equipped with the hydraulic control device.

FIG. 3 is a hydraulic circuit diagram provided with a conventional hydraulic control device.

[Explanation of symbols]

 Reference Signs List 10 aerial work platform 13 boom 16 hydraulic raising / lowering cylinder (hydraulic actuator) 18 switching valve (opening / closing valve) 20, 40 pressure compensating valve 30 check valve P hydraulic pump (hydraulic supply source)

Continuation of front page (56) References JP-A-4-248003 (JP, A) JP-A-5-19604 (JP, U) JP-A-61-98799 (JP, U) JP-A-3-4901 (JP , U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B66F 9/22 B66C 23/82

Claims (1)

(57) [Claims] A supply oil passage for supplying hydraulic oil from a hydraulic supply source to a hydraulic actuator; and an on-off valve provided in the supply oil passage for controlling supply of hydraulic oil from the hydraulic supply source to the hydraulic actuator. A drain oil passage branched from the hydraulic supply source and the on-off valve in the supply oil passage and connected to the tank; a pressure compensation valve provided in the drain oil passage for opening and closing the drain oil passage; A pilot oil passage for supplying a pilot pressure acting in a direction in which the pressure compensating valve closes, wherein the pilot oil passage is connected to the tank via the on-off valve when the on-off valve is in a closed state. A hydraulic control device configured to be connected to the hydraulic pressure source via the on-off valve when the on-off valve is in an open state; A check valve that allows only the flow of the fluid, and a predetermined amount that allows the hydraulic oil between the check valve and the pressure compensating valve to flow into the tank between the spool valve and the valve cylinder of the pressure compensating valve. A hydraulic control device characterized in that a gap is formed.